<!DOCTYPE html>
<html lang="en" xmlns:th="http://www.w3.org/1999/xhtml">
<head>
    <meta charset="UTF-8">
    <title>用户登录</title>
</head>
<body>
    <form action="/login" method="post">
        用户名&nbsp;&nbsp;:&nbsp;&nbsp;<input type="text" name="username"><br>
        密&nbsp;码&nbsp;&nbsp;:&nbsp;&nbsp;<input type="password" name="password"><br>
        <input type="submit" value="登录">
    </form>
    <!--unless时if的反义 为true就不显示-->
    <div style="color: red" th:unless="${#strings.isEmpty(msg)}" th:text="${msg}"></div>
</body>
</html>